Helping you Manage the Financial Details of Your Life



Decoding your Social Security Number

You are familiar with the three-part Social Security Number format: XXX-XX-XXXX.

But what do these numbers mean?

The first part is the Area Number. The second part is the Group Number, and the third part is the Serial Number.


Area Number – the first three digits

Social Security Numbers (SSN) issued before June 2011 were based on geography. If you were born prior to 1972, the first three digits stood for the state, territory or U.S. possession where you (or your parents) applied for your number. The numbering started in the northeast with the lowest numbers and moved west. If you were born after 1972, the Area Number indicated the state of residence shown on your SSN application. If your Social Security Number begins with, “001,” for example, you received your number while living in New Hampshire. If your number begins with “626,” you were in California.

As of June of last year, the Area Number is no longer based on geographical location. To combat spreading identity theft, the Social Security Administration (SSA) switched to a random-number system.

Some other changes:

  • In the past, numbers that began with an “8” were flagged for fraud. These are now valid.
  • Numbers that begin with “7” were once reserved for those in the Railroad Retirement System and non-U.S applicants. The Number “7” is now used for the general population.

No Social Security Numbers begin with “9,” “666” or “000.”


Group Number – the middle two digits

The Group numbers range from 01 to 99 and have no data significance. The SSA uses these to break Area Numbers into smaller blocks, making processing operations easier. Middle digits are never “00.”


Serial Number – the last four digits

Within each Group Number, Serial Numbers are assigned almost consecutively from 0001 through 9999. Serial Numbers begin with 0001 and continue in sequence, except every fifth SSN is given a Serial Number from the 2001-2999 series or the 7001-7999 series.  According to the SSA, issuing every fifth Serial Number from the 2000 or 7000 series “allows for scientific sampling of workers and beneficiaries.” The last four digits are never “0000.”


Why do we have this Numbering system?

When the Social Security Act of 1935 was passed, the government needed a system to keep track of what every person pays into Social Security over the course of his or her working life. Your Social Security number is life-long and unique. This is essential:  for you to receive the benefits you are entitled to, the SSA needs to keep an accurate record of the money you put in.

What happens to my SSN when I die?

According to the SSA, Social Security numbers are never reassigned.  When you die your SSN will be removed from the active files. The nine-digit numbering system allows for approximately one billion possible combinations. The SSA is confident that there will be sufficient numbers available for several generations to come.

Sources: American Institute of Professional Bookkeepers;; Social Security Bulletin, November 1982/Vol 45, No. 11;